a. Field of the Invention
This invention relates to methods for removing unreacted monomers from acrylic bulk polymerization slurries.
b. Description of the Prior Art
Acrylic polymers are conventionally manufactured by a suspension polymerization process, with the polymer solids subsequently being removed from the polymerization slurry by a filtration process. The polymers are then washed with water to remove unreacted monomers and are then dried. This process has the disadvantage that the polymer must be dried.
In one prior art method of removing unreacted monomers from a polymerization slurry, the slurry is allowed to cascade down a baffle type stripping column while steam is fed upward through the column, counter-current to the cascading slurry. Pluggage and fouling are reduced in this process but contact between the slurry and the steam is not as good as desired, resulting in reduced monomer stripping.
In the present invention neither water or steam is used, the slurry being contacted with heated solvent vapors to remove unreacted monomers. Mixers are used to insure good slurry solvent contact and the slurry is circulated through two mixing and separating stages in a particular manner to remove substantially all of the unreacted monomers. Polymer solutions from this process may be fed directly to a spinning machine without further treatment.